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Beyond the single-site approximation modeling of electron-phonon coupling effects on resonant inelastic X-ray scattering spectra
by Krzysztof Bieniasz, Steven Johnston, Mona Berciu
This Submission thread is now published as
Submission summary
| Authors (as registered SciPost users): | Krzysztof Bieniasz · Steven Johnston |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202108_00064v1 (pdf) |
| Date accepted: | 2021-09-09 |
| Date submitted: | 2021-08-26 07:51 |
| Submitted by: | Bieniasz, Krzysztof |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Resonant inelastic X-ray scattering (RIXS) is used increasingly for characterizing low-energy collective excitations in materials. RIXS is a powerful probe, which often requires sophisticated theoretical descriptions to interpret the data. In particular, the need for accurate theories describing the influence of electron-phonon ($e$-p) coupling on RIXS spectra is becoming timely, as instrument resolution improves and this energy regime is rapidly becoming accessible. To date, only rather exploratory theoretical work has been carried out for such problems. We begin to bridge this gap by proposing a versatile variational approximation for calculating RIXS spectra in weakly doped materials, for a variety of models with diverse $e$-p couplings. Here, we illustrate some of its potential by studying the role of electron mobility, which is completely neglected in the widely used local approximation based on Lang-Firsov theory. Assuming that the electron-phonon coupling is of the simplest, Holstein type, we discuss the regimes where the local approximation fails, and demonstrate that its improper use may grossly \textit{underestimate} the $e$-p coupling strength.
Author comments upon resubmission
Thank you for forwarding the reports of the Referees who examined our work. We are encouraged by their apparent interest in our work, and we thank them for their valuable comments.
Below you will find a list of changes that we have made to our manuscript and our point-by-point responses to the two reviewers. We feel that we have addressed their comments and are resubmitting our paper for publication in SciPost.
Thank you for your consideration.
Sincerely,
Drs Krzysztof Bieniasz, Steven Johnston, and Mona Berciu
List of changes
1. We have inserted a reference to an earlier work discussing the diagrammatic expansions associated with our level of MA modeling.
2. We clarified that our MA modeling captures an indirect RIXS process.
3. We have added an explanation of why MA is considered a variational method.
4. In response to Referee #1, we have introduced a new paragraph following Eq.(20) that summarizes the main steps in calculating the RIXS cross-section. We also added a new paragraph in the Introduction mentioning the generalization of this approach to study electron-magnon couplings, together with two appropriate new references.
5. We have corrected the typos, missing references, and missing definitions for acronyms noted by Referee #1.
6. In response to Referee #2, we have added a paragraph in the Introduction explaining where MA is accurate (basically, everywhere except in the strongly adiabatic limit), and mentioned recent numerical work extending its applicability into the extreme adiabatic limit (new Ref. [38]).
Published as SciPost Phys. 11, 062 (2021)
Reports on this Submission
Report #1 by Anonymous (Referee 2) on 2021-9-2 (Invited Report)
- Cite as: Anonymous, Report on arXiv:scipost_202108_00064v1, delivered 2021-09-02, doi: 10.21468/SciPost.Report.3487
Report
I am satisfied with the authors' responses to my report and their changes to the paper. This is an extremely clear and well written article, and I enjoyed reading it.
I understand the diagrammatic approach was already developed in a previous work and the authors don't believe it worth including such a figure here (presumably because it would be identical to fig 2 of ref 36). However I think it might be worth reemphasising just below Eq 16 the link between the 'single site impurity' of ref 36 and the core hole potential of this work, so interested but non-expert readers can make the link straight away.